The only real problem I see with this is that zombie mode now uses the multiplayer engine. This means it's now protected by VAC, thus making it that much harder to hack for.

With WaW and BO it was easy since the SP.exe was never protected by VAC, but with BO2 they have changed everything. From a dev point of view I'd say it was a smart move, not only for allowing more player, but also to fight hacking. Non the less, zombie mode really sounds quite interesting this time round.

The only real problem I see with this is that zombie mode now uses the multiplayer engine. This means it's now protected by VAC, thus making it that much harder to hack for.

With WaW and BO it was easy since the SP.exe was never protected by VAC, but with BO2 they have changed everything. From a dev point of view I'd say it was a smart move, not only for allowing more player, but also to fight hacking. Non the less, zombie mode really sounds quite interesting this time round.

bad to hear zombie will be VAC protected hope there will be much working undetected hacks for zombie...

Not if you are planning to make a trainer using code injection. If you make a trainer based on your previous zombie trainers I can guarantee you will get VAC banned.
Zombies won't be an option in the SP.exe anymore it will now be part of the mp.exe. Mark my words, the next batch of zombie trainers will either get you banned very fast or will be extremely limited in features.